Process of preparing aqueous dispersion of an acrylonitrile interpolymer and a thermosetting resin and product obtained



Dec. 30, 1958 P. F. SANDERS 2, 5

PROCESS OF PREPARING'AQUEOUS DISPERSION OF AN ACRYLONITRILE INTERPOLYMERAND A THERMOSETTING RESIN AND PRODUCT OBTAINED Filed,April 16, 1956DEIONIZED 0R DISTILLED WATER SODIUM META BISULFITE- SODIUM LAURYLSULFATE ION EXCHANGE J, A. AORYLONITRILE RESIN coLuma a. HETHACRYLICACID M HouocEmzmc somuu I POTASSIUM FIRST sues PER Wm LAURYL AMMONIAOALS 1, SULFATE AQUEOUS S J m SOLUTION l AMMONIA P TANK sscouo STAGEAMMONIACAL 55 T065 TANK usumuzmou SNGLE T GE T0 pH VALUE UP TO L J v i II NEUTRALIZATION ;""7" .DEIONIZED 0R DISTILLED T0 pH VALUE OPTIONALWATER I 5 .5 T080 POLYMERIZATION sscouo STAGE ADDITION 1 REACTOR 0FDISPERSING AGENT. WATER-DILUTABLE,HEAT-REACTIVE PHENOL/FORHALDEHYDERESIN FILTER \I/ AMMONIACAL uzumuzmc HEAT mmmc MIXER.

FINAL FILTER PRODUOT STORAGE INVENTOR PHILIP F. SANDERS AGENT PROCESS OFPREPARING AQUEOUS DISPERSION OF AN ACRYLONITRILE INTERPOLYMER AND ATHERMOSETTING RESIN AND PRODUCT OBTAINED Philip F. Sanders, Glen Mills,Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del.,a corporation of Delaware Application April 16, 1956, Serial No. 578,40514 Claims. (Cl. 260-293) This invention relates to aqueous dispersioninterpolymer compositions. More particularly the invention relates tostabilized aqueous dispersion compositions comprising ammonium salts ofcertain acidic acrylonitrile interpolymers characterized bypackage-stability and resistance to gelation and to a method ofpreparing these ammoniacal aqueous dispersions.

In copending United States patent applications Sanderson Serial No.369,890 and Sanders Serial No. 369,969, both filed July 23, 1953, now U.S. Patent No. 2,787,603, are described useful acidic interpolymersprepared from a monomer mixture consisting of acrylonitrile, an alphaolefinic monocarboxylic acid selected from the group consisting ofacrylic acid, methacrylic acid, ethacrylic acid, phenyl acrylic acid andcrotonic acid, and an ester of at least one of these acids with asaturated aliphatic monohydric alcohol having from 1 to 8 carbon atoms;and useful coating and impregnating compositions comprising such acidicinterpolymers. For many coating purposes, it was found desirable tomodify the acidic interpolymer in the form of an aqueous dispersion witha water-dilutable, heat-reactive phenol/formaldehyde resin. In applyingthese aqueous dispersion compositions to metal substrates, such as inthe case of wire-coating, best results ordinarily are obtained when thecoating composition at the time of use is adjusted to a pH value in therange of about 9.0 to 10.0 with ammonium hydroxide or a volatile amine.

Although these aforementioned aqueous dispersions of acidicinterpolymers, either in the acidic state or ammoniacally adjusted tothe indicated high pH value, can be satisfactorily applied to a widevariety of substrates to provide useful coated or impregnated articles,these dispersions have certain undesirable deficiencies pertinent topackaging and storage. The acidic dispersions ordinarily cannot bepackaged in conventional metal containers and must be stored in glass orin metal containers interiorly protected with a coating inert toward theaqueous dispersion in order to prevent contamination with corrosionproducts. Even when packaged in an appropriate container, the acidicdispersions are not as storage-stable as is ordinarily desired forcommercial use. These acidic dispersions develop coagulum andfine-particle-size polymer grit during storage, particularly whenmechanical shearing conditions, such as pumping and high speedagitation, is involved in handling the material. 'Another deficiency ofthese acidic dispersions is that they are at a viscosity lower than thatordinarily desired for most uses.

The ammoniacally adjusted dispersions can be stored and subjected topumping and agitation without development of coagulum or polymer grit,but these dispersions are lacking in viscosity-stability and resistanceto gelation.

The rate of viscosity-increase 'of these dispersions is so rapid thatthe material stored for a period as short as .mixture of polymerizablemonomers 2,866,763 Patented Dec. 30, 1958 several weeks is either gelledor at a viscosity too high for application by ordinary means.

The primary object of this invention is to overcome the describeddeficiencies of the aqueous dispersions of the aforementionedinterpolymers. An important object of this invention is to provideimproved aqueous dispersion interpolymer compositions of theaforementioned class of interpolymers characterized by superiorviscosity-stability,

package-stability and resistance to gelation. Another object is toprovide an aqueous dispersion interpolymer composition of the describedclass stably advanced in viscosity. A further object is to provide amethod of preparing ammoniacal aqueous dispersion interpolymers of amonomer mixture consisting of acrylonitrile, an alpha olefinicmonocarboxylic acid selected from the group consisting of acrylic acid,methacrylic acid, ethacrylic acid, phenyl acrylic acid and crotonicacid, and,

an ester of at least one of these acids with a saturated aliphaticmonohydric alcohol whereby the resulting aqueous dispersion ischaracterized by viscosity-stability, package-stability and resistanceto gelation. Other important objects will become apparent as thedescription of the invention proceeds.

These and other important objects are accomplished by preparing anaqueous dispersion of an ammonium salt of an acidic interpolymer byinitially preforming the acidic interpolymer by emulsion polymerizationin water of a consisting of (A) 30% to by weight of acrylonitrile, (B)1.5% to 15% by weight of at least one alpha-olefinic mo-nocarboxylicacid selected from the group consisting of acrylic acid, methacrylicacid, ethacrylic acid, phenyl acrylic acid and crotonic acid, and (C) 15to 65% by weight of at least one ester of an acid of (B) with asaturated aliphatic monohydric alcohol having from 1 to 12 carbon atoms,

forming an ammonium salt of the interpolymer by men-- tralizing theresulting aqueous dispersion of the acidic interpolymer at a temperaturein the range of about 45 C. to C. with ammonium hydroxide in an amountsufiicient to neutralize at least 10% by weight of the acidic (B)component of the interpolymer and provide. the aqueous dispersion with apH value in the range'ofselected from the group consisting ofphenol/formalde-- hyde resin, urea/formaldehyde resin,melamine'/formalde-- hyde resin, urea/melamine/formaldehyde resin andmixtures thereof with the aqueous dispersion of the interv polymer ineither its acid-form or its ammonium saltform, either prior to theheat-effected ammoniacal re-' action or with the ammoniacal aqueousdispersion interpolymer composition subsequent to the heat-effectedneutralization.

The drawing is a flow-sheet of a of the process of the invention.

The following specific examples represent the best preferred embodimentmodes contemplated for carrying out the invention which.

are given by way of illustration and not limitation. The parts andpercentage figures are basis unless stated otherwise.

expressed on a weight Potassium persulfate solution, 5.0% by wt. in

distilled water 2.08

The sodium meta bisulfite (Na S O had an assay of 97.5% and acorresponding content of at least 65.58% 80;.

The sodium lauryl sulfate was the commercial available DuponoP C havingan assay of at least 90%, the remainder being 1.5% to 3.5% of unsulfatedfatty alcohol and not more than 8% of a mixture of sodium chloride andsodium sulfate.

The potassium persulfate (K S O had an assay of at least 94% and acorresponding content of at least 70% S 0 The acrylonitrile monomer aspurchased contained 250 to 300 parts per million of organic amines as apolymerization inhibitor. These amine inhibitors were removed by passingthe inhibited acrylonitrile through a column of Amberlite IR-120 ionexchange resin in its acid form.

The methacrylic acid monomer was the commercially available glacialgrade which contained hydroquinone at a concentration of about 1000parts per million as an inhibitor. This monomer was used without removalof the inhibitor.

The butyl acrylate monomer as purchased contained hydroquinone at aconcentration of about 100 parts per million as an inhibitor. Thismonomer was also used without removal of the inhibitor.

In the preparation of the interpolymer dispersion, all the indicatedcomponents except the potassium persulfate solution were charged into ahigh speed homogenizing mixer, emulsified for about 6 minutes andtransferred to a reactor equipped with means for controlled temperaturevariation and means for agitation. The emulsified charge was heated to60 C. While it was adequately agitated with an agitator rotating atabout 200 R. P. M. When the charge reached 60 C., the potassiumpersulfate solution, freshly prepared by dissolving the salt in water atabout 45 C., was added to the preheated charge. The initiatedpolymerization reaction was exothermic and heat was withdrawn from thereaction mixture in order to hold the temperature at about 60 C.Polymerization was continued until the exothermic reaction was no longerdetectable; about 143 minutes after the addition of the persulfate. Theproduct was held at a temperature of 60 C. for 90 minutes additional andcooled to room temperature. Analysis of product samples taken at thisstage showed a non-volatile content of 34.5% by weight, indicating thatthe monomer conversion was at least 98.5%.

The resultingaqueous dispersion of, the acidic interpolymer had a pHvalue of 3.8 and was characterized by an average particle size of..22micron. .The interpolymer separated from the aqueous dispersion wascharacterized by a relative viscosity of 6.6 as determined with an A. E.T. M. #200 ostwald-Cannon-Fenske viscosimeter at 25 C. using dimethylformamide as the solvent for preparing the viscosity test solutionat0.5% by weight of the interpolymer.

This unstabilized aqueous dispersion interpolymer product of Example 1was filtered through felt and divided into aliquot portions which weretreated respectively as follows with the final composition ineachinstance 4 adjusted with distilled water to a non-volatile contentof 30% by weight.

Sample A.-Diluted with distilled water without any other treatment.

Sample B.-The aqueous dispersion product neutralized to a pH value of9.0 with ammonium hydroxide and diluted.

Sample C.Diluted with distilled water, heated to C. in about 5 minutes,held at this temperature for 15 minutes and immediately cooled to roomtemperature.

Sample D.-Ammoniacally neutralized to a pH value of 7.5, heat treated at75 C. as described for sample C and immediately cooled.

Sample E.Treated as described for sample D except that the ammoniacalneutralization was to a pH value of 9.0.

Sample F.-Heat-treated as described for sample C and thereafterammoniacally neutralized to a pH value of 9.0.

Sample G.Initially neutralized to a pH value of 7.5 with ammoniumhydroxide, heat-treated as described for sample D and thereafterammoniacally neutralized to a pH value of 9.0.

The viscosity of these respective samples was determined at 25 C. usinga Broolifield viscosimeter operating at 6 R. P. M. with a #2 spindle.The samples were then stored in an oven at 50 C., periodically removedfrom the storage oven, cooled to 25 C. and measured for viscosity todetermine the effect of storage at 50 C. on viscosity stability. Whenthe viscosity increased beyond the practical range of the #2 spindle,other standard spindles were used with the Brookfield viscosimeter.

The viscosity data for these samples recorded in centipoises are shownin Table 1.

Table 1 EFFECT OF STORAGE A'I 50 0. ON VISCOSITY STABILITY SampleViscosity A a o D Initial 20 20 28 days. 20 1, 000 20 00 42 days- 2012,000 20 00 50 days. 20 as, 000 30 00 80 days... 55 00, 000 120 soBtdayss0 Gelled 120 50 102 days. 7000 10,000 50 10tdays. 50

The data in Table 1 show that sample D, representing ammoniacalneutralization of the acidic dispersion product to a pH value of 7.5followed by heat-treatment was outstandingly stable in viscosity. Thissample did not gel or significantly increase in viscosity during oneyear of storage. This sample remained package-stable and free ofcoagulation and formation of fine grit polymer. While the data forsamples A and C show moderate viscosity stability for the aqueousdispersion interpolymer composition in its unneutralized state, thesesamples were not package-stable and heating did not provide an advancein'the initial viscosity. The aged samples showed coagulation anddevelopment of fincgrit polymer.

Sample B exhibited a desirable initial viscosity, but the product wasunstable in viscosity and bodied during 28 days of storage to aviscosity impractical for use. Sample E, equivalent to sample B butheat-treated, was advanced to a high initial viscosity impractical foruse and gelled more rapidly than sample B.

Data for samples F and G show that when the alkalinity of theheat-treated aqueous dispersion interpolymer composition in either itsacidicform or ammonium resin.

salt-form is subsequently ammoriiacally adjusted to ,a pH value of 9.0,the products were unstable in viscoslty.

For many coating and impregnating purposes, the aqueous dispersioninterpolymer composition is desirably modified with a water-dilutable,heat-reactive aldehyde condensation resin, such as phenol/formaldehydeSince this preferred modifier is heat-reactive, another series of thefollowing samples was prepared from the filtered aqueous dispersionproduct of Example 1 to ascertain the effect of ammoniacalneutralization and heat-treatment of the aqueous interpolymer dispersionin admixture with the heat-reactive resin. In all samples, thephenol/formaldehyde resin, identified as Bakelite BR-15100 resincontaining 66% non-volatile resin dispersed in water, was used in theproportion of 11 parts dry weight per 100 'parts dry weight of theinterpolymer.

Sample H.The mixture of the aqueous dispersion product of Example 1 andBR-15100 resin was neutralized to a pH value of 7.5 with ammoniumhydroxide, heated in 5 minutes to 75 C., held at this temperature for 15minutes and immediately cooled to room temperature.

Sample I.-This sample was prepared as described for sample H andthereafter adjusted to a final pH value of 9.0 with ammonium hydroxide.

Sample J.This sample was prepared as described for sample H except thatthe heat-treatment at 75 C. was extended to 30 minutes.

Sample K.-The acidic aqueous dispersion product of Example 1 wasammoniacally neutralized to a pH value of 7.5, heated to 75 C. in 5minutes, held at this temperature for 15 minutes, the BR-15100 resin wasblended therein and the resulting composition immediately cooled to roomtemperature.

Sample L.The acidic aqueous dispersion product of Example 1 was blendedwith the BR-15100 resin, the resulting composition was heated in 5minutes to 75 C., held at this temperature for 15 minutes, andthereafter immediately cooled to room temperature. The pH value of thisproduct which had no ammoniacal treatment was 5.1.

Sample M.This sample was the same as sample L except that it wasammoniacally adjusted to a final pH value of 9.0.

Sample N.-The process of preparing this sample was the same as that usedfor sample H except the mixture of the acidic aqueous dispersion ofExample 1 and BR-15100 resin was ammoniacally neutralized to a pH valueof 9.0 prior to the heat-treament.

The viscosity of these respective samples, each diluted to anon-volatile content of 30% by weight with distilled water, was measuredwith the Brookfield viscosimeter at 25 C. and 6 R. P. M. to establish aninitial value and periodically measured at 25 C. after storage at 50 C.The resulting viscosity data reported in centipoises are shown in Table2.

Table 2 EFFECT OF STORAGE AT 50 0. ON VISCOSITY STABILITY SampleViscosity V H I I 1 K 1 L M I N 40 20 80 ("80 2o 0 220 700 10 20 2801.600 10 20 sec act-0 10 20 440 7, 000 10 580 26,000 10 10 1, 240Geller] 10 10 1.300 10 10 9,000 10 Gelled The data in Table 2 show thatsamples H, l, K and L are resistant to gelation for a period of at least164 days at 50 C. Of these, sample L was lacking in package stabilitybecause of continued coagulation and growth of polymer grit duringstorage. Samples which were adjusted to a pH value of 9.0 rapidlyincreased in viscosity during storage and gelled within the 164 daystest period.

The data show that the phenolic resin can be blended with the aqueousdispersion interpolymer composition either before or after theheat-efiected ammoniacal reaction without altering the stability of theproduct. A comparison of the data for samples H and I show that theheat-reactive phenol/formaldehyde resin is advantageously blended withthe aqueous dispersion interpolymer composition prior to the ammoniacalneutralization when it is desirable to provide the composition with anadvanced viscosity which is stable.

EXAMPLE 2 Parts by wt. Unstabilized aqueous dispersion interpolymercomposition, .41% by wt. in water 70.40

Water-dilutable, heat-reactive phenol/ formaldehyde resin, BR-15100, 66%by wt. in water 4.85 Ammonium hydroxide, 29% NH .70 Distilled water .Q24.05

The unstabilized aqueous dispersion interpolymer composition wasprepared as described in Example 1 using the same relative proportionsof the respective monomers, that is, acrylonitrile 63%, butyl acrylate32% and methacrylic acid 5%. The polymerizable mixture consisted of thefollowing composition:

The emulsion polymerization was carried out at 60 C. The monomerconversion was 98.8% and the aqueous dispersion product had a polymercontent of 41.0%. The pH value of the aqueous dispersion was 3.7 at 25C. and the average particle size of the interpolymer in the dispersionwas ;25 micron. The interpolymer had a relative viscosity of 6.3 usingdimethyl formamide as the solvent. The unstabilized acidic aqueousinterpolymer dispersion was filtered through felt before it was used in'the preparation of the product of Example 2. I

The indicated content of ammonium hydroxide cor-' responds to theapproximate amount added to raise the pH value of the acidic aqueousdispersion at 3.7 to an ammoniacal alkalinity of 7.65.

The component of the composition of Example 2 were blended at roomtemperature until uniform. The result ing mixture was heat processed asfollows: (a) heated in 5 minutes to 45 C., (b) heated in another 5minutes to 65 C., (c) heated in another 5 minutes to C. and thereafterheld at this latter temperature for.120 minutes. Samples were taken at45 'C., 65 C., 85 C. and at intervals while the temperature was held at85 C. The viscosity data reported in centipoises for these samplesmeasured at 25 C. using the Brookfield viscosim eter at 6 R. .P. Maareshown in Table 3.

r Table 3 mECT .OF. HEATING TIME ON VISCOSITY ADVANCE- MENT Sample:Viscosity 3 Original 30 (a) Afterheating to 45 C. in 5 minutes 65 (b)After heating to 65 C. in minutes 110 (0) After heating to 85 0m minutes210 (d) Thereafter holding at 85 C. for 10 minutes 245 (e) Thereafterholding at 85 C. for

minutes 235 (f) Thereafter holding at 85 C. for

. minutes 235 (g) Thereafter holding at 85 C. for 60 minutes 210 (h)Thereafter holding at 85 C. for 90 minutes 170 (i) Thereafter holding at85 C. for 120 minutes 170 These data show that the ammoniacallyneutralized aqueous dispersion product can be heated for a relativelyshort period of time to provide a desirable viscosity advance. Prolongedheating caused the viscosity'of the productto level off at a value belowthe maximum viscosity-advance observed.

These samples were package-stable, viscosity-stable andgelation-resistant during storage at room temperature for a period of atleast one year.

Part 2: Ammonium hydroxide 29% NH;, to pH value 5.5 to 6.5 0.15 Part 3:

Water-dilutable, heat-reactive phenol/formaldehyde resin, BR-l5100, 6%by wt. in water 6.45 Water, deionized 21.30 Part 4: Ammonium hydroxide29% NH to pH value 7.2 1.00

Total enamel 128.90

The components were the same as those used in Examples l and 2.

'Part 1 representing the unstabilized aqueous dispersion interpolymercomposition was prepared following the process described forthepreparation of the aqueous dispersion product of Example 1, carryingout the emulsion polymerization at about 60 C. The resulting aqueousdispersion product had a pH value of 3.8, an average particle diameterof about 0.20 micron, and an interpolymer content of 37.5% by weight.The polymer had a relative viscosity of 6.5 using dimethyl formamide asthe solvent.

After completion of the polymerization inpart 1, the resulting acidicaqueous dispersion interpolymer composition while at the temperature ofabout 60 C. was neutralized with the ammonium hydroxide of part 2 to apH value in the range of 5.5 to 6.5. The added amount of ammoniumhydroxide was sufficient to neutralize at least 10% by Weight of themethacrylic acid component of the interpolymer. The combined parts 1 and2 were filtered through felt, transferred to a storage tank as anintermediate product for subsequent use and allowed to cool to roomtemperature. In the ammoniacal neutralization stage, the combined parts1 and 2 ordinarily are exposed to an elevated temperature in the rangeof 45 C. to 60 C. for about 30 minutes or longer. Completion of thisintermediate ammoniacal product consisting of combined parts 1 and 2represents a preferred and convenient point of interruption in thecommercial manufacturing process. This intermediate product isviscosity-stable and storage-stable. It is adequately low in viscosityfor convenient filtering and it can be reheated, cooled and subjected tomechanical operations, such as agitation and pumping, after filtrationwithout introducing fine-grit formation or coagulation.

When preparation of the final product of Example 3 Was resumed, part 3was blended with the intermediate product; that is, the combined parts 1and 2 which had been filtered and stored, combined parts 1, 2 and 3 wereheated to 87 C. with agitation and part 4 was added thereto as a secondstage ammoniacal neutralization to adjust the composition to a pH valueof 7.2. The total amount of ammonium hydroxide of parts 2 and 4 wassufiicient to neutralize approximately 90% by weight of the methacrylicacid component of the interpolymer. The resulting mixture was agitatedat 120 R. P. M. for 70 minutes Without either supplying heat oraccelerating the cooling. Thereafter the product was cooled to roomtemperature and filtered to remove any coarse foreign matter, such aspolymer skins.

The drawing showing a diagrammatic flow-sheet of the invention processis representative of the steps in the process described above for thepreparation of the product of Example 3. The flow sheet indicates theoperative optional single stage am'moniacal neutralization which can beused in place of the preferred two stages of ammoniacal neutralization.The flow-sheet also indicates the optional second stage of addition ofsodium lauryl sulfate dispersing agent which is described in thepreparation of the product of Example 4.

Alternatively, the process for preparing the product of Example 3 canconsist of the indicated steps without cooling and storing theintermediate product. The filtered product of the first-stage ammoniacalneutralization can be transferred warm or hot to the final product mixerfor blending with the heat-reactive phenol/formaldehyde resin,second-stage ammoniacal neutralization and heattreatment for stablyadvancing the viscosity.

The resulting stabilized product exhibited excellent package-stabilityand viscosity-stability while stored at 45 C. (40 F.) and 25 C.respectively for one year and stability for at least 8 months whenstored at 50 C.

For use as a wire coating, the resulting product of Example 3 having anon-volatile content of 32.5% by weight as determined by weighing theresidue after heating a 1 gram sample for two hours at C., was adjustedto a pH of 9.3, and diluted with deionized water to a non-volatilecontent of 21% by weight. This ammoniaeal aqueous dispersion wire enamelcomposition was applied to No. 18 A. W. G. copper wire in six coats at acoating speed of 1.4 feet per minute using a conventional verticaldip-coating bath for the aqueous enamel. Prior to each immersion of thewire into the coating bath, it was pre-wet by immersion in a 1% aqueoussolution of sodium lauryl sulfate serving as a wetting agent tofacilitate wetting of the copper wire with the aqueous dispersion wireenamel. After each withdrawal from the enamel coating bat-h, the coatedwire was heated by passing it through an oven having an average airtemperature of about 221 C. (425 F.). The path of the coated wirethrough the oven was 12 feet in length; hence each successive coat ofenamel was subjected to about 51 seconds exposure to the oventemperature. The six coats of enamel increased the diameter of the wireby '9 3 mils, that is, the thickness of the coating on the coppersubstrate was 1.5 mils.

Another sample of the same No. 18 copper wire was coated at a coatingspeed of 26 feet per minute using the same aqueous dispersion wireenamel composition adjusted to a pH value of 9.3 with ammonium hydroxideand diluted with deionized water to a non-volatile content of 13% byweight. The successive coats of applied enamel were cured by passagethrough an oven having an average air temperature of 315 C. (600 F.) anda heating path of 12 feet. Each successive coat was exposed for about 28seconds to the oven temperature. At the indicated coating speed andnon-volatile content of the aqueous enamel, the 6 coats of cured wireenamel increased the diameter of the wire by 3 mils.

A sample of No. 25 A. W. G. copper wire was also coated with 4 coats ofthe product of Example 3 similarly adjusted to a pH value of 9.3 anddiluted to a nonvolatile content of 15% by weight with deionized water.This aqueous composition was applied at a coating speed of 35 feet perminute and the successive coats were each cured by passage through apath of 4 feet in an oven having an average air temperature of 455 C.(850 B). Each successive coat was exposed for about 7 seconds to thisoven temperature. The four coats of wire enamel increased the diameterof the wire by 2 mils.

The resulting respective samples of coated wire were evaluated inaccordance with NEMA and other standardized tests accepted and used bythe electrical industry and were found to be equivalent to controlsamples of wire coated in the same manner using the equivalent aqueousdispersion interpolymer wire enamel composition which had not beensubjected to ammoniacal neutrali zation and heat-treatment in accordancewith the practice of this invention. Wires coated with the product ofExample 3 exhibited a smoother surface than that of the insulatingcoating on the control wire. The product of Example 3 was coatable onwire at higher speeds without depositing a rough uneven coating on thewire in comparison with the control enamel.

Copper wire coated with the product of Example 3 was successfully usedin winding motors and transformers. The resulting motors were found tobe particularly serviceable in the presence of fluorinated refrigerants,such as Freon-22 monochlorodifiuoromethane. I

The product of Example 3 was also satisfactorily applied to square andrectangular cross-section copper wire as well as to the conventionalwire of circular crosssection.

EXAMPLE 4 Parts by wt. Water, deionized 63.93 Sodium metal bisulfite0.02

Sodium lauryl sulfate, Duponol C solution,

The components of this composition were the same as those used in thepreceding examples. The mixture of monomers corresponded to 35%acrylonitrile, 5% methacrylic acid and 60% butyl acrylate for a total of100% by weight of the mixture of monomers.

The process of preparing the interpolymer by emulsion polymerizationfollowed the process described in Example I, initially charging all butthe last two components.

into a homogenizing mixer to emulsify the charge and transferring theemulsion to the reactor. The charge was heated to about 60 C. and thepotassium persulfate was added, initiating an exothermic reaction. Heatliberated during this reaction which lasted about two hours waswithdrawn to maintain the temperature at about 60 C. Fifteen minutesafter the addition of the potassium persulfate, the second addition ofsodium lauryl sulfate was made. Addition of the sodium lauryl sulfatewas made in two stages in order to moderate the reaction rate and tocontrol the particle size of the resulting dispersion. After theexothermic reaction subsided, the composition was maintained at about 60C. for one hour, neutralized at this temperature with ammonium hydroxideto a pH value of 6.0, heated to a temperature of C., held at thistemperature for'one hour and cooled to room temperature.

The resulting aqueous dispersion interpolymer product had an averageparticle diameter of about 0.11 micron. The polymer had a relativeviscosity of about 3.8 This product was viscosity-stable andstorage-stable over a period of at least 9 months at room temperature.

The product of Example 4 was successfully used to impregnate mats ofnon-woven fibers of Orlon acrylic fiber laid down as a waterleaf bypaper-making methods. The resulting dry web impregnated with 26% byweight of the interpolymer derived from the aqueous dispersion andweighing 3.8 grams total for an 8" x 8" square was found to providealmost greater bursting strength and 60% greater tear strength thanconventional kraft paper of the same weight, when tested by TappiStandard Methods T-403 M53 and T-414 M-49.

This product was also used to impregnate a mat of nonwoven glass fiberswhich initially weighed 4 ounces per square foot. The weight ratio offiber to the interpolymer binder was 1.6 to 1.0 of binder. The resultingimpregnated mass was dried for 30 minutes at 107 C. (225 F.) andthereafter pressed at p. s. i. for 10 minutes at 205 C. (400 F.). Theresulting product was a rigid panel about .045 inch thick. This rigidstructure exhibited high dielectric strength and was useful asslot-liners for motors and generators. The rigid structure was alsouseful as structural panelling where resistance to solvents and vaporswere required. Solvent resistance was enhanced for these impregnatedstructural units where the aqueous dispersion composition of Example 4included 5% to 10% of a Water-dilutable heat-reactivephenol/formaldehyde resin such as BR-15100 based on the weight of theinterpolymer.

While the specific examples describe preferred viscosityadvancedammoniacal aqueous dispersion tripolymers derived from acrylonitrile,butyl acrylate, and methacrylic acid monomers as representative of thepractice of the invention, numerous other aqueous dispersions of theacidic interpolymers of acrylonitrile can be similarly stabilized andviscosity-advanced in the ammonium salt form. For example, the acidicmonomer component of the interpolymer can be any alpha olefinicmonocarboxylic acid selected from the group consisting of methacrylicacid, acrylic acid, ethacrylic acid, phenyl acrylic acid and crotonicacid or mixtures thereof. Any of these acidic monomers can besubstituted on an equal weight basis for the methacrylic acid monomerused in the preparation of the described interpolymers in the examples.The acidic monomer component can be present in any amount ranging fromabout 1.5% to 15%, preferably about 2% to about 10% by weight based onthe total weight of the mixture of monomers. Among these acidiccomponents, methacrylic acid is particularly preferred.

' While the particularly preferred ester monomer component of the acidicinterpolymer is butyl acrylate, other esters of acrylic acid with asaturated aliphatic monohydric alcohol having from 1 to 12 carbon atomscan be substituted wholly or in part for the indicated amount of butylacrylate monomer in the preparation of the interpolymers described inthe examples. Other acidic interpolymers operative in the practice ofthis invention can also be prepared from monomer mixtures in which theester monomer component, present in an amount ranging from 15% to 65% byweight of the monomer mixture, is at least one ester of a saturatedaliphatic monohydric alcohol having from 1 to 12 carbon atoms with analpha olefinic monocarboxylic acid selected fro-m the group consistingof acrylic acid, methacrylic acid, ethacrylic acid, phenyl acrylic acidand crotonic acid. Representative 1 to 12 carbon atom alcohols includemethyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isobutylalcohol, hexyl alcohol, cyclohexyl alcohol, octyl alcohol and laurylalcohol.

The acrylonitrile monomer content of the monomer mixture used in thepreparation of the acidic acrylonitrile interpolymer can range from 30%to 80% by weight.

The emulsion polymerization in the preparation of the interpolymers canbe carried out by any conventional emulsion methods, using a redoxinitiator. The bisulfite/ persulfate redox initiator mixture isparticularly preferred. While the weight ratio of potassium persulfateto sodium meta bisulfite can range from 1:1 to 10:1, optimum results areobtained when the ratio is about 2 to 5 parts of the persulfate per partof the bisulfite. The preferred proportion of this redox initiator is inthe range of about 25% to 50% based on the weight of the mixture ofmonomers although a proportion as high as 1.0% on said basis can besatisfactorily used. The presence of traces of iron contamination in thepolymerizable charge is desirable for activation of the redox initiator.A trace of iron concentration in the range of about 0.5 part to about10.0 parts per million of the charge is preferred. Trace coppercontamination functions similarly. Raw materials used ordinarily providetotal amounts of iron and copper within thi preferred range. At iron andcopper trace concentrations lower than 0.5 p. p. m., the exothermicreaction time of polymerization is significantly extended and atconcentrations higher than 10.0 p. p. m., activa' tion becomes tooaccelerated to be practical at 60 C. However, this acceleratedactivation of the redox initiator can be used to advantage when thepolymerization is carried out at lower temperatures.

While 60 C. is a particularly preferred operating temperature forcarrying out the emulsion polymerization, temperatures in the range of50 C. to 70 C. are ordinarily most suitable. The polymerization can becarried out at room temperature and at temperatures as low as about 0 0,above the freezing temperature. Temperatures higher than 70 C. can beused, but operations must be carried out under pressure when thetemperature exceeds the boiling point of any one of the monomers. Thereactions are difiicult to control at these higher temperatures.

The dispersing agent used in the emulsion polymerization is preferablysodium lauryl sulfate and it is preferably used in the proportions of0.30% to 1.50% based on the weight of the mixture of monomers. However,a proportion in the range of 0.2% to 4.0% on said basis is operative.()ther alkali m etal salts of fatty alcohol sulfates,non-ionicdispersing agents and mixtures thereof can be used in place ofthe sodium lauryl sulfate.

In the described examples,the emulsion polymerization was carried out inthe presence of the amount of hydroquinone inhibitor ordinarily presentin the monomers as purchased,that is, the total hydroquinone content wasin the range of about 25, to 40 p. p. m. based on the totalpolymerization charge. However, polymerization is operative over therangeof 0 to 100 parts of hydroquinone per million of charge.Inhibitor-free monomers of butyl acrylate and methacrylic acid can beobtained by vacuum distillation. .A concentration of the inhibitorgreater than 40 p. p. m. causes a lengthening of the exothermic reactiontimeand a decrease in the relative viscosity of the interpolymer.Monomethyl ether of hydroquinone is occasionally used in place ofhydroquinone as a polymerization inhibitor. No distinction is observedbetween the use of this inhibitor and hydroquinone.

Beta, beta-imino-dipropionitrile was the major component of the organicamine mixture used to inhibit one commercial grade of acrylonitrilemonomer in an amount ranging from 250 to 300 p. p. m. based on themonomer. This inhibitor significantly retarded the redox initiatedpolymerization. While the polymerization is operable in the presence ofthis amount of amine inhibitors contributed by the inhibitedacrylonitrile monomer, complete removal of this inhibitor is preferred.Removal of the inhibitors i best accomplished by passage of thisamine-inhibited acrylonitrile monomer through a column of ion-exchangeresin Amberlite IR- regenerated to H-form (acid-form). Alternatively,the amine inhibitors can be removed by adding 1% of orthophosphoric acidto the acrylonitrile monomer to react with the amine and thereafterdistilling the acrylonitrile at atmospheric pressure.

The monomer concentration in the aqueous polymerizable charge ispreferably in the range of 25% to 45% by weight. While higherconcentrations up to 70% are operative, coagulation losses makeoperations at concentrations above 50% impractical or prohibitive.

The water specified in the examples is preferably of distilled,deionized or demineralized quality. This is to eliminate or minimize theeffect of chemical compounds normally present in tap water on thepolymerization reaction. Tap water having a low content of suchcompounds can be used.

Agitation during emulsion polymerization is preferably carried outwithin the range of to 300 R. P. M., but any speed which providesadequate heat transfer and maintains uniform dispersion of the monomersin the aqueous emulsion is operative. Ordinarily this requires agitationat a speed within the range of 50 to 400 R. P. M. Higher speeds areundesirable because many interpolymer dispersions coagulate or coalesceunder mechanical shear.

The polymerization charge is preferably emulsified as a homogeneouspremix prior to charging into the polymerization reactor. A particularlysuitable homogenizer for premixing is the Eppenbach homo-mixer. Themodel of this mixer used was comprised of a multi-bladed rotor having arotor/ stator clearance in the range of about .030 to about .0625 inchand rotated with a peripheral speed of about 60 feet per second. Thehomogenized premix ordinarily is stable against phase separation for atleast about 60 minutes at 60 C. Hence, agitator speed in thepolymerization reactor is less critical and serves primarily to providegood heat transfer when the process includes the step of high speedhomogeneous premixing.

The polymerization reaction period is preferably in the range of 75 to150 minutes, as measured by the duration of the exothermic reaction, toassure adequate heat-trans fer. Rate of heat dissipation ordinarilyprovided in commercial operations practically limits the exothermicperiod to at least 60 minutes in commercial operations. Exothermicreaction periods beyond about 6 hours are con sidered to beimpractically long.

Aqueous dispersion interpolymers, as represented by Examples 1, 2 and 3prepared by emulsion polymerization under the aforementioned preferredoperating conditions, ordinarily have a particle size in the range ofabout .10 to .30 micron and the interpolymer is characterized by aweight average molecular weight, as deter mined by light scattering, inthe range of about 300,000 to 800,000. The relative viscosity of theseinterpolymers based on a 0.5% solution in dimethylformamide ordinarilyranges from about 4.0 to 10.0.

Emulsion polymerized interpolymers derived from monomer mixtures inwhich the weight proportion of the acrylic ester predominates over theacrylonitrile, as

13 represented by Example 4, ordinarily are characterized by a relativeviscosity in the range of 2.5 to 5.0 in dimethylformamide and theaverage particle size of the interpolymer in the aqueous dispersion isin the range of about .05 to .15 micro In neutralizing the acidicaqueous dispersion interpolymer compositions with ammonium hydroxide toprovide the composition with viscosity-stability, resistance to gelationand package-stability, a suflicient amount of ammonium hydroxide isadded to the acidic aqueous dispersion, which ordinarily is at a pHvalue no greater than about 4.0, to increase the pH value to at leastabout 5.5. This amount of ammonium hydroxide ordinarily added to reachthis pH value is sufiicient to convert at least by weight of the acidiccomponent of the interpolymer to its ammonium salt. At a pH value in therange of 5.5 to 6.5, the ammoniacal aqueous dispersion composition isnot highly advanced in viscosity over the unneutralized acidic aqueousdispersion and it is most convenient to separate undesirable coagulumand fineparticle-size polymer grit from the dispersion at thisammoniacal stage, such as by filtration.

If separation of the coagulum and polymer grit is delayed until afterammoniacal heat-treatment at a higher pH value, such as in the range of6.7 to 8.0, whereby the viscosity is significantly advanced, the removalof the coagulum and polymer grit is more difiicult to accomplish byordinary means practical for commercial operations. If the separation iscarried outwith the acidic aqueous dispersion prior to the stabilizingammoniacal neutralization to a pH value of at least 5.5, polymer gritand coagulum continues to form during storage under acidic conditionscorresponding to a pH value less than 5.5. Hence, in commercialoperations, two stage ammoniacal neutralization is preferred with 'aseparation or filtration step between the two ammoniacal stages. In theinitial stage, the ammoniacal neutralization is carried out to a pHvalue of 5.5 to 6.5 and in the second stage the ammoniacalneutralization is advanced to a pH value in the range greater than thatof the first stage up to 8.0, preferably in the range of 6.7 to 7.5. Thetotal amount of ammonium hydroxide ordinarily added is sufiicient toconvert from 50% to about 100% by weight of the acidic component of theinterpolymer to its ammonium salt.

Under operating conditions which provide for am moniacal heat-treatmentof the acidic aqueous dispersion interpolymer immediately afterpolymerization, the addition of ammonium hydroxide can be made as asingle stage, separating the coagulum and polymer grit from the acidiccomposition prior to the ammoniacal neutralization.

In the heat-treatrnent of the ammoniacal aqueous dispersion interpolymercomposition, the temperature can range from about 45 C. to about 95 C.The heating period can range from about 5 minutes to about '4 hours. Thepreferred heat-treatment ranges from about 15 minutes to about 120minutes at a temperature ranging from about 65 C. to about 90 C. Heatingfor a period as short as 5 minutes within these temperature rangesordinar'ily provides viscosity-advancement of at least 50% over that ofthe untreated aqueous dispersion.

When ammoniacal neutralization is in two stages, heating in the initialneutralization stage is not critical as viscosity-advancement is not'theprimary object of the initial stage. In this initial ammoniacalneutralization, the ammonium hydroxide can be added at the temperatureexisting after-completion of the emulsion polymerization, thistemperature being in the range of room temperature to about 70 C. andordinarily at least about 45 C. The second stage ammoniacalneutralization to a pH value in the range of 6.7 to 8.0 accompanied withfurther heating represents the pertinent viscosity-advancing stage.

When the aqueous interpolymer dispersion is modified withwater-'dilutable heat-reactive aldehyde condensation 14 resins, such asa heat-reactive phenol/formaldehyde resin, the modifier can be blendedwith the interpolymer dispersion either before or after the ammoniacalheat-treatmentor between the first and second stage of ammoniacalneutralization. Blending prior to the heat-treatment is preferred as theentire composition is thereby stabilized rather than just the componentinterpolymer dispersion.

The particularly preferred method of preparing the final enamel from theacidic aqueous dispersion interpolymer composition and the heat-reactivealdehyde con densation resin includes the steps of first stageammoniacal neutralization of the acidic dispersion at a temperature inthe range of 45 C. to 65 C. to a pH value of 5.5 to 6.5, filtering,blending the partially neutralized aqueous dispersion with theheat-reactive aldehyde condensation resin, second stage ammoniacalneutralization to a pH value in the range of 6.7 to'7.5, heating at atemperature in the range of 65 C. to C. to viscosityadvance thecomposition and cooling to room temperature. Ordinarily the finalproduct is filtered to remove any coarse coagulum formed by drying outof interpolymer dispersion on parts of the heat-treating equipment.

While the examples illustrate modification of the acrylonitrileinterpolymer dispersion with a water-dilutable heat-reactivephenol/formaldehyde resin, other waterdilutable, heat-reactive aldehydecondensation resins selected from the group consisting ofurea/formaldehyde resin, melamine/formaldehyde resin, urea/melamine/formaldehyde resin, phenol/formaldehyde resin, and mixtures thereof canbe substituted on an equal weight basis for the phenol/ formaldehyderesin in the examples. When these heat-reactive resins are used tomodify the interpolymer dispersion, the amount can vary from about 2% toabout 40% based on the Weight of the interpolymer. A proportion of theseresins in the range of 5% to 20% on the indicated basis is preferred.

Water-soluble coalescing agents are desirable components of the aqueousdispersion compositions when applied at room temperature as anair-drying coating or impregnant. The presence of a coalescing agentordinarily is not required where the applied coating is baked at hightemperatures sufiicient to bring about coalescence. The content ofacrylonitrile in the interpolymer has a pertinent eitect on the need fora coalescing agent. When the acrylonitrile content is low, ordinarilythere is no need for the coalescing agent, but when the acrylonitrilecontent is high, suchas 65% to 80% by weight of the interpolymer, acoalescing agent is required in applications where the dry coating isnot baked. Cyclic ethylene carbonate, tetramethylene sulfone, ethyleneglycol monoethers of 1 to 4 carbon atom saturated aliphatic monohydricalcohols, diethylene glycol monoethers of l to 4 carbon atom saturatedaliphatic monohydric alcohols, diacetone alcohol, dimethylformamide anddimethylacetamide are representative water-soluble coalescing agentswhich can be included in the aqueous dispersion interpolymercomposition. The amount of water-soluble coalescing agent can be presentin amounts up to based on the weight of the dispersed interpolymer inthe final composition, but ordinarily the presence of the coalescingagent is avoided during the ammoniacal heattreating step.

The stabilized aqueous dispersion interpolymer com positions can befurther modified with pigments, fillers, extenders; finely-dividedwater-swellable hydrous silicates such as bentonite and montmorilloniteclays, dyes and compatible film-forming resins and plasticizers. Ifdesired, the compositions of this invention can be adjusted at the timeof use to a higher ammoniacal pH value in the range of 8.0 to 10.0 withammonium-hydroxide or volatile amines. In some applications, this higheralkalinity provides improved Wetting of the sub- 'strate.

The aqueous dispersion compositions of this invention can contain asmuch as 50% by weight of dispersed ammonium salt of the acidicinterpolymer and as little as Ordinarily the practical content ofammoniacal interpolymer is-in the range of to 45% by weight.

These aqueous dispersion interpolymer compositions can be applied by anyof the conventional methods ordinarily used in coating or impregnatingwith aqueous dispersion products. The applied coatings or impregnantscan be dried or cured at temperatures ranging from room temperature tobaking temperatures as high as 500 C.

The stabilized aqueous dispersion interpolymer compositions have wideutility in the coating and impregnating fields. They provide excellentbaking finishes for electrical wire insulation. They provide excellentairdrawing finishes for wood, such as on bowling alleys and bowlingpins. They can be applied to metallic and nonmetallic substrates eitheras baking or air-drying finishes. They are particularly useful asimpregnants for fabrics and non-woven webs prepared from syntheticfibers such as derived from polyacrylonitrile, ethylene terephthalatepolyester polymers, nylon, viscose rayon, polyurethane,polytetrafluoroethylene and polyvinylidene chloride. They can also beused to coat or impregnate products prepared from natural fibers such ascotton, jute, ground wood pulp and chemical wood pulp. They are alsouseful for coating and impregnating woven fabric and non-woven websprepared from glass fibers. When used as the impregnant for non-wovenwebs, the proportion of dry weight impregnant to fiber can be varied toprovide useful products ranging in properties from those of thinpaper-like sheets or leather-like products to thick rigid panels.

This invention otters a significant advance in the art in providingcommercially acceptable ammoniacal aqueous dispersion interpolymer saltcompositions which are characterized by package-stability,gelation-resistance and viscosity-stability. This invention alsoprovides for the preparation of stable aqueous dispersion interpolymercompositions desirably advanced in viscosity.

While there are above disclosed but a limited number of embodiments ofthe structure, process and product of the invention herein presented, itis possible to produce still other embodiments without departing fromthe inventive concept herein disclosed, and it is desired therefore thatonly such limitations be imposed on the appended claims as are statedtherein, or required by the prior art.

The embodiments of the invention in which an exclusltive property orprivilege is claimed are defined as folows:

l. A process for preparing a package-stable and gelation-resistantaqeuous dispersion interpolymer composition which process comprisespreforming, by emulsion polymerization in water, an acidic interpolymerof a mixture of monomers consisting of (A) to 80% by weight ofacrylonitrile, (B) 1.5% to 15% by weight of at least one alpha olefinicmonocarboxylic acid selected from the group consisting of acrylic acid,methacrylic acid, ethacrylic acid, phenyl acrylic acid and crotonicacid, and (C) 15% to 65% by weight of at least one ester of an acid of(B) with a saturated aliphatic monohydric alcohol having from 1 to 12carbon atoms, forming an ammonium salt of said interpolymer byreactingthe acidic (B) component of the interpolymer with arm monium hydroxideat a temperature in the range of about C. to about 95 C., and coolingthe ammoniacal dispersion to a temperature below about 30 C., the amountof ammonium hydroxide, introduced being sufiicient to provide theaqueous dispersion with a pH value in the range of 5.5 to 8.0. a

2. The process of claim 1 wherein said ammoniacal reaction mixture ismaintained within said temperature range for a period ranging from 5minutes to 4 hours r 16 prior to cooling, whereby a stable advance inviscosity is imparted to the aqueous dispersion.

3. The process of claim 1 wherein the amount of ammonium hydroxide issufficient to form an ammonium salt corresponding to reaction with atleast 10% by weight of the acidic (B) component of the interpolymer.

4. The process of claim 1 wherein the amount of ammonium hydroxide issufiicient to form an ammonium salt corresponding to reaction with atleast 50% by weight of the acidic (B) component of the interpolymer.

5. The process -of claim 1 wherein said mixture of monomers consists ofacrylonitrile, methacrylic acid and butyl acrylate.

6. The process of claim 1 wherein said ammoniacal reaction is carriedout in two stages with a separation step between the initial stage andthe second stage, to remove coagulum and polymer grit, the reaction insaid initial stage being at a pH value in the range of 5.5 to about 6.5,the second stage reaction subsequent to said separation step beingcarried out at a temperature in the range of 45 C. to 95 C. withsufficient ammonium hydroxide being present to provide the aqueousdispersion with a pH value in the range of greater than that of thefirst stage up to 8.0.

7. The process of claim 6 which includes, prior to said second stageammoniacal reaction, the step of blending with the aqueous dispersioninterpolymer composition, a water-dilutable, heat-reactive aldehydecondensation resin selected from the group consisting ofphenol/formaldehyde resin, urea/formaldehyde resin,melamine/formaldehyde resin, urea/melaminelforrnaldehyde resin andmixtures thereof in an amount ranging from about 2% to 40% based on theweight of said interpolymer.

8. The process of claim 7 wherein said water-dilutable, heat-reactivealdehyde condensation resin is phenol/formaldehyde resin.

9. The process of claim 6 which includes, subsequent to said initialstage of ammoniacal reaction and prior to said second stage ofammoniacal reaction the step of blending with the aqueous dispersioninterpolymer composition, a water-dilutable, heat-reactive aldehydecondensation resin selected from the group consisting ofphenol/formaldehyde resin, urea/formaldehyde resin,melamine-formaldehyde resin, urea/melamine/formaldehyde resin andmixtures thereof in an amount ranging from about 2% to 40% based on theweight of said interpolymer.

10. The process of claim 9 wherein the heat-effected ammoniacal reactionof said second stage is carried out by heating at a temperature in therange of 65 C. to 90 C. for 15 to 120 minutes.

11. A process for preparing a gelation resistant, viscosity-stable andpackage-stable aqueous dispersion interpolymer composition Which processcomprises the steps of forming a homogeneous premix compositioncomprising water, sodium lauryl sulfate, sodium meta bisulfite and amixture of monomers consisting of (A) 30% to by weight of acrylonitrile,(B) 1.5% to 15% by weight of methacrylic acid, and (C) 15% to 65% byweight of butyl acrylate, emulsion-polymerizing said homogeneous premixin the presence of potassium persulfate added to complete in combinationwith the bisulfite a redox initiator, forming an ammonium salt of theacidic interpolymer by adding ammonium hydroxide to the resultingaqueous dispersion of the acidic interpolymer to a pH value in the rangeof-5.5 to 6.5 as a first stage ammoniacal reaction, filtering theresulting ammoniacal aqueous dispersion, mixing said filtered dispersionwith a water-dilutable, heat-reactive phenol/formaldehyde resin,

further adding ammonium hydroxide to the resulting mix ture to a pHvalue in the range of about 6.7 to about 7.5 as a second stageammoniacal reaction, maintaining the product of said second stagereaction at a temperature in the range of 65 C. to C. for a periodranging from 15 minutes to about 120 minutes and cooling to atemperature below about 30 C. V

12. The process of claim 11 wherein the amount of ammonium hydroxideadded in the first stage ammoniacal reaction is sufiicient to convert atleast by weight of the methacrylic acid component (B) of theinterpolymet to its ammonium salt and the total amount of ammoniumhydroxide added in the first and second stages of ammoniacal reaction issuflicient to convert at least 50% by weight of the methacrylic acidcomponent (B) of the interpolymer to its ammonium salt.

13. The process of preparing a package-stable, gelation-resistant,heat-bodied aqueous dispersion interpolymer composition comprising thesteps of: (a) preforming an aqueous acidic interpolymer dispersioncomposition by initially preparing an aqueous dispersion polymerizationcharge consisting essentially of water, a mixture of polymerizablemonomers consisting of (A) 30% to 80% acrylonitrile, (B) 1.5% to of atleast one alpha olefinic monocarboxylic acid selected from the groupconsisting of acrylic acid, methacrylic acid, ethacrylic acid, phenylacrylic acid and crotonic acid, and (C) 15% to 65% of at least one esterof an acid of (B) with a saturated aliphatic monohydric alcohol havingfrom 1 to 12 carbon atoms per molecule, and from .2% to 4% of an alkalimetal salt of an acidic fatty alcohol sulfate ester based on the weightof said polymerizable monomers, the concentration of said mixture ofmonomers being from about 25% to about 50% of said aqueous charge, andefiecting polymerization of said polymerizable monomers the presence ofabout 25% to 1% of a vinyl polymerization initiator based on the weightof said monomers at a temperature from about C. to about C. for a periodsufiicient to provide the resulting interpolymer with a relativeviscosity of from about 2.5 to 10 based on a 0.5% solution in dimethylformamide, (b) forming an ammonium salt of said dispersed acidicinterpolymer resulting from step (a) by adding ammonium hydroxidethereto in an amount sufiicient to adjust said aqueous interpolymerdispersion to a pH value of 5.5 to 6.5 and reacting the resultingmixture at a temperature from about 45 C. to about 70 C., (c) filteringthe product of step (b), the aqueous dispersion of said interpolymerammonium salt being the filtrate, (d) further adding ammonium hydroxideto said filtered dispersion in an amount suflicient to adjust saidaqueous dispersion to a pH value of 6.7 to 8, (e) heating the productaqueous dispersion of the resulting interpolymer ammonium salt at atemperature from 65 C. to C. for a period of about 15 to minutes, and(f) cooling the product dispersion to room temperature below 30 C.

14. The aqueous interpolymer ammonium salt dispersion product of theprocess of claim 13.

References Cited in the file of this patent UNITED STATES PATENTS1,981,102 Hagedorn et al. Nov. 20, 1934 2,557,266 Dittmar et al. June19, 1951 2,582,303 Wohnsiedler et al. June 15, 1952 2,772,166 FowlerNov. 27, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 2,866,763 December 30, 1958 Philip F Sanders of the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 3, line 68, for "A. E. T, M." read A. S. T. M. column 6, line 40,for "26,10" read 26.10 column '7, line 48, for "6% by Wt." read 66% byWt. column 11, line 27, for "50%" read .50% column 15, line 17, for"drawing" read drying column 18, line 1, for 25%" read 25% Signed andsealed this 21st day of April 1959.

(SEAL) Attest:

KARL H. AXLINE Attesting Oflicer ROBERT C. WATSON Commissioner ofPatents

1. A PROCESS FOR PREPARING A PACKAGE-STABLE AND GELATION-RESISTANTAQUEOUS DISPERSION INTERPOLYMER COMPOSITION WHICH PROCESS COMPRISESPREFORMING, BY EMULSION POLYMERIZATION IN WATER, AN ACIDIC INTERPOLYMEROF A MIXTURE OF MONOMERS CONSISTING OF (A) 30% TO 80% BY WEIGHT OFACRYLONITRILE, (B) 1.5% TO 15% BY WEIGHT OF AT LEAST ONE ALPHA OLEFINICMONOCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF ACRYCLIC ACID,METHACRYLIC ACID, ETHACRYLIC ACID, PHENYL ACRYCLIC ACID AND CROTONICACID, AND (C) 15% TO 65% BY WEIGHT OF AT LEAST ONE ESTER OF AN ACID OF(B) WITH A SATURATED ALIPHATIC MONOHYDRIC ALCOHOL HAVING FROM 1 TO 12CARBON ATOMS, FORMING AN AMMONIUM SALT OF SAID INTERPOLYMER BY REACTINGTHE ACIDIC (B) COMPONENT OF THE INTERPOLYMER WITH AMMONIUM HYDROXIDE ATA TEMPERATURE IN THE RANGE OF ABOUT 45*C. TO ABOUT 95*C., AND COOLINGTHE AMMONIACAL DISPERSION TO A TEMPERATURE BELOW ABOUT 30*C., THE AMOUNTOF AMMONIUM HYDROXIDE INTRODUCED BEING SUFFICIENT TO PROVIDE THE AQUEOUSDISPERSION WITH A PH VALUE IN THE RANGE OF 5.5 TO 8.0.